1. Field of the Invention
The present invention relates to a single-blow pneumatic hand tool for inserting t-nuts, and in particular to a pneumatic hand tool for inserting t-nuts having prongs.
2. Description of Background Art
The first commonly available t-nuts were stamped fasteners with a hollow shaft with an internal thread and a flange without prongs. These t-nuts had holes in the flange (usually three) that could accept small nails that would be used to hold the t-nut to the work piece. Later (late 1930's or early 1940's) t-nuts were introduced with prongs that were formed from the flange. These t-nuts would be located over the hole in a work piece and driven into the work piece with a hammer.
In the late 1960s, an “auto-sta” octagonal flange 4-prong t-nut, designed to feed in a track of a machine, and a t-nut machine to drive these t-nuts into the work piece, was developed. Today while a significant percentage of t-nuts are inserted using machinery, a substantial market remains where t-nuts are driven into a work piece by hand using a hammer. Specific areas where t-nuts are inserted with a hammer are:
Small Volume User: Traditional t-nut machines are generally only cost effective when the volume of t-nuts exceeds 50,000, for example.
Assembly Line Insertion: Some companies believe it to be more cost effective to insert t-nuts on the line while the frame is being assembled.
T-nuts in Large Work Pieces: Large work pieces are difficult to handle. In modem furniture production, frames are typically cut from large plywood sheets. When the components are large they can be too big and awkward to manipulate into a t-nut insertion machine.
Work Pieces with Blind Holes: In some applications t-nuts are inserted in a blind hole, such as when used to mount a leveler on a chair leg.
More recently, a pneumatically operated hand tool for inserting t-nuts has been introduced. This device has a magazine that accepts t-nuts that are collated into strips with a flexible adhesive tape, and uses a pneumatic stapler body with a reversed action. When the tool is at rest, the driver is fully extended in the down position and the tip of the driver sticks out the bottom of the nose piece. To operate the tool, the tip of the driver is first placed in the hole. Pressing down on the tool then releases the trigger safety. Squeezing the trigger initiates the following sequence: (1) The driver retracts, a t-nut is advanced into the nose of the tool by a feeder mounted on the magazine; and (2) When the trigger is released, the driver descends, driving the t-nut into the work piece.
While the concept of this pneumatically operated hand tool provides some improvement, the tool disclosed therein requires a careful technique during use to ensure that the t-nut is set into the hole properly. A problem often occurs because the driver is used to locate the hole, and squeezing of the trigger retracts the driver. The recoil of that action often causes the tool to move slightly. As a result, the t-nut is very often driven into the side of the hole, making it very difficult to start a screw in the t-nut. By holding the tool a certain way, it is possible to compensate for the recoil and to drive t-nuts properly, but for many users and environments it has never worked satisfactorily. A further problem with conventional single-blow (single-shot) hand tools is that they typically require a secondary safety to prevent injury. Even with a secondary safety, conventional single-blow hand tools cannot completely eliminate the risk of injury to the operator.
To address the problem of risk of injury to operators of single-blow hand tools, multi-blow hand tools have been proposed. While multi-blow hand tools may address the problem of injury associated with single-blow hand tools, they are slower to operate than single-blow tools.
An advantage of the single-blow hand tool is one of speed, particularly in the case where the user of the hand tool is inserting a large number of fasteners. The drive cycle with a single-blow tool is practically instantaneous compared with the 1 to 2 seconds that may be required with the multi-blow hand tool. Also when used continuously in a high volume application, the constant vibration of the multi-blow hand tool compared to the single-blow hand tool would lead to operator preference for the single-blow tool.
On the other hand, the pneumatic motor on the single-blow tool is larger, more powerful and more complex than that used on the multi-blow tool, and for this reason generally is more costly to manufacture. However, for a high volume user, the additional cost will not likely present an obstacle.
Thus, a need exists for a hand tool that is both fast and safe. The present invention was developed to address the problems of the conventional art including the problems described above.